Posted: Fri Jul 21, 2006 12:06 pm Post subject:
Researching maximum life span of the power supply of a small satellite.

For use in a private scientific project I'm researching how long a
small earth orbiting satellite will operate. The satellite's
electronics needs to generate for over 30 seconds 15 watts of power
each day.

I'm not scientific/technical educated so please excuse me for saying
stupid things. The project is still in a hypothetical stage so don't be
afraid to tell it won't work.

I'm aiming at a life span of 100 years! Is this possible? For
engineering reasons I want to minimize the use of solar cells.

A good quality solar cell panel of 25 square centimeters (10 square
inches) will generate about 15 watts of energy. Solar cells have a
durability of some 40 years. But by light-induced degradation (LID) the
effectiveness of the cells will slowly degrade. Can this problem be
solved if you use a 3 times as big (75 square centimeters/ 30 square
inches) solar panel covered for 2/3 and shift this covering each 40
years to expose a new set of solar cells?

Other options are.

Extreme durable batteries
The longest shelf life of batteries are about 20 years.
(http://www.raytechcatalog.com/product_info/code-red-batteries-20-year-shelf-life-1-pair-142.html).
This is accomplished by keeping the electrolyte separate of the plates
until the battery is activated. Can this shelf life be expanded? By
lowering the temperature for example? How long will such a battery give
an amount of energy of a daily 15 watts over 30 seconds?

Fuel cells;
A fuel cell is also very durable. 40,000 hours for stationary
applications (wikipedia.org). 100 years*30 seconds = 305 hours. Or will
the electrolyte chemicals just like normal batteries degrade after a
few decades? The amounts of fuels like hydrogen and oxygen will be
quite a lot I think.

Atomic batteries:
Most satellites and space probes make use of nuclear. These batteries
are extremely durable. Even the Radioisotopic Thermoelectric Generator
of the space probe voyager 1 still makes some 300 watts ( at launch
date 1977 it generated 470 watts) after 29 years of use. But nuclear
devices are the least desirable choice of power supply for a small
satellite orbiting the earth. If the satellite burns up in the
atmosphere the nuclear elements will cause a very dangerous pollution.
However this is an example of a very small nickel-63 battery wich will
give electrical energy for over some 50 years! The power specs (volt,
amperes, watts) are not given.
http://www.news.cornell.edu/releases/Oct02/cantilever.ws.html